Bose Sound System

Hello all, I just bought a super TT Coupe (silver) from 12/98. According to the seller there is the Bose sound system in it. But I’m not so sure anymore. It’s a lot loud, but not very distortion-free. So how can I see if there are really the Bose sound system or just the normal speakers in it?? (feeling kind of stupid, that to questions 😉 Before thank you for your help!